Israel has imposed a blockade on the Palestinian territories, after an apparently coordinated series of attacks killed at least 26 Israelis.

Palestinian leader Yasser Arafat, under strong international pressure to arrest those behind the suicide bombings, declared a state of emergency in the West Bank and Gaza.

This is a moment where the advocates for peace in the
Middle East must rise up and fight terror

George W Bush

And United States President George W Bush, in talks with Israeli Prime Minister Ariel Sharon in Washington, called on the Palestinian Authority to arrest immediately those behind the attacks.

The violence began on Saturday night when 10 young Israelis and two suicide bombers were killed in Jerusalem. Hours later, at least 15 people died when a bus was ripped apart by a bomb in the port of Haifa.

BBC Washington correspondent Tim Franks says that as far as the US is concerned, the balance of responsibility in the region has shifted.

There has been no indication that the Americans have, as following previous attacks, called for Israeli restraint in their response.

Both leaders left the Washington talks in sombre mood without making a statement, as Mr Sharon cut short his visit to return home to deal with the crisis.

WEEKEND ATTACKS:

Saturday night: Suicide attacks and car bomb in Jerusalem

Sunday: Two gunmen kill Israeli in Gaza

Suspected gunmen pursued and killed by Israeli forces

Explosion on bus in Haifa

But earlier, US Secretary of State Colin Powell told the CBS network: "We're not about to tell Mr Sharon what he should do."

And Defence Secretary Donald Rumsfeld appeared to back Israel's policy of assassinating Palestinian militants - previously condemned by Washington.

"The only way to defend against terrorists is to go after the terrorists," he said.

Arafat blamed

The militant group Hamas claimed that it carried out the attacks, but the Israeli Government immediately blamed Mr Arafat and put a block on all non-essential Palestinian traffic in areas of the West Bank outside Palestinian control.

The Israeli cabinet is to hold an emergency meeting on Monday to decide on new measures to combat the violence, a senior Israeli official said.

The Palestinian leadership issued a strongly-worded statement, condemning the attacks and pledging to track down those responsible.

The Palestinian Authority said its security forces would pursue anyone planning or carrying out attacks against Israeli civilians and bring them to justice.

Any group acting against the authority's decision will be banned, it said.

The violence has wrecked an American peace mission to the region, BBC correspondents say.

Teenagers killed

On Saturday night in Jerusalem's Ben Yehuda area cafes and restaurants were packed with teenagers.

Two suicide attacks and a car bombing in quick succession killed 10 people and injured 170, most of them young revellers.

Nail bombs are designed to create maximum carnage

Twenty minutes later, a car bomb exploded in a nearby side street, sending screaming survivors running in all directions.

As the violence continued into Sunday, Palestinian gunmen killed at least one Israeli and wounded five others at a Jewish settlement in Gaza.

Israeli forces later killed the gunmen.

At lunchtime, a suicide bomber blew up a bus in the northern coastal city of Haifa, killing 15 people and wounding more than 100 others.

The bus was travelling through a mixed neighbourhood, where Arabs live alongside Jews, when the attack happened.

People rushed into the street to help the wounded, call for ambulances, and cover the dead.

Hours after the Jerusalem blasts, Israeli forces arrested several alleged militants in the village of Abu Dis on the outskirts of the city.

Palestinian police arrested a top member of Islamic Jihad, Mohammed al-Hindi, after a gun battle at his Gaza home on Saturday.

Hamas and Islamic Jihad have threatened to avenge Israel's killings of prominent militants.

Condemnation and messages of sympathy came from around the world, with Jordan urging Israel to show restraint in the interests of peace.

Egypt strongly condemned the attacks, as did France, Russia and many other countries.

Israeli Foreign Minister Shimon Peres, describing the wave of attacks as "one of the worst ... ever seen", summoned all foreign ambassadors to an emergency meeting.